Poly(Alkyl Glycidate Carbonate)s as Degradable Pressure-Sensitive Adhesives

New Chemistries for Degradable Pressure-Sensitive Adhesive Networks

With the increasing use of pressure-sensitive adhesives (PSAs) in various industries, there is a need for greater sustainability, particularly in developing polymer materials from renewable resources, as well as the reuse and recycling of materials to reduce environmental impact, reduce waste, or extend their life. Here, we outlined the required properties of PSAs which are governed by the molecular parameters (molecular weights, dispersities, molecular weight between entanglement, molecular weight between cross-links and gel content) of polymer materials which subsequently define the physical properties (storage and loss moduli, glass transition temperature) that are required for good performance in peel, tack and shear tests. The sustainable approach discussed here is the development of degradable polymer materials featuring selectively degradable linkages in the backbone. This provides a viable alternative for the design of PSAs that could overcome the 'stickies' problem and make the recycling of glass and cardboard more efficient.

Biomass-Derived Optically Clear Adhesives for Foldable Displays

Novel acrylate monomers, derived from terpenes are synthesized for use in optically clear adhesives (OCAs) suitable for foldable displays. These OCAs are prepared using visible-light-driven polymerization, an eco-friendly method. Through physical, rheological, and mechanical characterization, the prepared OCAs possess low modulus and exhibit outstanding creep and recovery properties, making them suitable for foldable devices.

Fluorescent Carbon Dioxide-Based Polycarbonates Probe for Rapid Detection of Aniline in the Environment and Its Biomarkers in Urine

Aniline compounds, as a class of widely used but highly toxic chemical raw materials, are increasingly being released and accumulated in the environment, posing serious threats to environmental safety and human health. Therefore, developing detection methods for aniline compounds is of particular significance. Herein, we synthesized the fluorescent third monomer cyano-stilbene epoxide M and ternary copolymerized it with carbon dioxide (CO2) and propylene oxide (PO) to synthesize carbon dioxide-based polycarbonate (PPCM) with fluorescence recognition functions, as well as excellent performance, for the first time. The results revealed that the PPCM fluorescent probe exhibited typical aggregation-induced luminescence properties and could be quenched by aniline compounds. The probe presented anti-interference-specific selectivity for aniline compounds, and the detection limit was 1.69 × 10-4 M. Moreover, it was found to be a highly sensitive aniline detection probe. At the same time, the aniline biomarker p-aminophenol in urine could also be detected, which could expand the potential applications of polymers in the fluorescence-sensing field.

Degradable, Ultraviolet-Crosslinked Pressure-Sensitive Adhesives Made from Thioester-Functional Acrylate Copolymers

Pressure-sensitive adhesives (PSAs) are made from soft, irreversibly lightly crosslinked polymers. Even after removal from surfaces, they retain insoluble networks which pose problems during the recycling of glass and cardboard. Herein, degradable PSAs are presented that provide the required performance in use but have networks that can be degraded after use. A series of copolymers was prepared through radical copolymerization of n-butyl acrylate, 4-acryloyloxy benzophenone (ABP) photo-crosslinker, and dibenzo[c,e]oxepin-5(7H)-thione (DOT) to provide degradable backbone thioesters. The optimum tack and peel strengths were found for molar contents of 0.05 mol% ABP and 0.25 mol% DOT. Degradation of the backbone thioesters through aminolysis or thiolysis led to the full dissolution of the networks, loss of adhesive properties of films (decreases in the measured tack and peel strengths), and the quick detachment of model labels from a substrate. Inclusion of DOT into PSAs offers a viable route toward degradable and recyclable packaging labels.

Synthetic Pressure Sensitive Adhesives for Biomedical Applications

Pressure sensitive adhesives are components of everyday products found in homes, offices, industries, and hospitals. Serving the general purpose of fissure repair and object fixation, pressure sensitive adhesives indiscriminately bind surfaces, as long as contact pressure is administered at application. With that being said, the chemical and material properties of the adhesive formulation define the strength of a pressure sensitive adhesive to a particular surface. Given our increased understanding of the viscoelastic material requirements as well as the intermolecular interactions at the binding interface required for functional adhesives, pressure sensitive adhesives are now being explored for greater use. New polymer formulations impart functionality and degradability for both internal and external applications. This review highlights the structure-property relationships between polymer architecture and pressure sensitive adhesion, specifically for medicine. We discuss the rational, molecular-level design of synthetic polymers for durable, removable, and biocompatible adhesion to wet surfaces like tissue. Finally, we examine prevalent challenges in biomedical wound closure and the new, innovative strategies being employed to address them. We conclude by summarizing the progress of current research, identifying additional clinical opportunities, and discussing future prospects.

Effects of Alkyl Ester Chain Length on the Toughness of PolyAcrylate-Based Network Materials

Polyacrylate-based network materials are widely used in various products owing to their facile synthesis via radical polymerization reactions. In this study, the effects of alkyl ester chains on the toughness of polyacrylate-based network materials were investigated. Polymer networks were fabricated via the radical polymerization of methyl acrylate (MA), ethyl acrylate (EA), and butyl acrylate (BA) in the presence of 1,4-butanediol diacrylate as a crosslinker. Differential scanning calorimetry and rheological measurements revealed that the toughness of MA-based networks drastically increased compared with that of EA- and BA-based networks; the fracture energy of the MA-based network was approximately 10 and 100 times greater than that of EA and BA, respectively. The high fracture energy was attributed to the glass transition temperature of the MA-based network (close to room temperature), resulting in large energy dissipation via viscosity. Our results set a new basis for expanding the applications of polyacrylate-based networks as functional materials.

Robust Construction of Supersmall Zwitterionic Micelles Based on Hyperbranched Polycarbonates Mediates High Tumor Accumulation

Despite the numerous advantages of nanomedicines, their therapeutic efficacy is hampered by biological barriers, including fast in vivo clearance, poor tumor accumulation, inefficient penetration, and cellular uptake. Herein, cross-linked supersmall micelles based on zwitterionic hyperbranched polycarbonates can overcome these challenges for efficiently targeted drug delivery. Biodegradable acryloyl/zwitterion-functionalized hyperbranched polycarbonates are synthesized by a one-pot sequential reaction of Michael-type addition and ring-opening polymerization, followed by controlled modification with carboxybetaine thiol. Cross-linked supersmall zwitterionic micelles (X-CBMs) are readily prepared by straightforward self-assembly and UV cross-linking. X-CBMs exhibit prolonged blood circulation because of their cross-linked structure and zwitterion decoration, which resist protein corona formation and facilitate escaping RES recognition. Combined with the advantage of supersmall size (7.0 nm), X-CBMs mediate high tumor accumulation and deep penetration, which significantly enhance the targeted antitumor outcome against the 4T1 tumor model by administration of the paclitaxel (PTX) formulation (X-CBM@PTX).

Biodegradable epoxy thermosetting system with high adhesiveness based on glycidate-acid anhydride curing

Biodegradable epoxy thermosets were developed by curing through copolymerization of a diglycidate monomer, a bifunctional epoxide bearing ester linkages, with cyclic acid anhydrides as a biosafe thermosetting system. The cured products of the glycidate exhibit high adhesiveness, identical to analogous cured products of conventional glycidyl ethers. Even an inert cycloolefin polymer and polyimide can be adhered. The cured products of the glycidate can be hydrolytically and biologically degraded. The biodegradation of the glycidate thermoset in compost completely proceeded within 2 weeks.

Glycidate as a High-Strength Epoxy Adhesive Curable with Amine under Ambient Conditions

This paper reports that glycidates bearing epoxy moieties with adjacent ester can be cured with diethylenetriamine (DETA) under mild conditions and exhibit high adhesiveness. Curing of bifunctional glycidates with DETA gave cross-linked products. The curing started at a lower temperature (7 °C) than the analogous glycidyl ether (27 °C), while the rate of the curing was slower due to the lower activation energy (E_a = 57 kJ/g) and exothermicity (ΔH = 58 J/g) as confirmed by DSC analysis. The curing system of neopentyl glycol diglycidate and DETA effectively adhered aluminum plates by curing at 25 °C, and the strength was more than five times higher than the curing with analogous glycidyl ether. The higher adhesive strength under curing of ambient conditions and facile preparation of monomers are the significant advantages of this curing.

Sustainable glycerol terpolycarbonates as temporary bioadhesives

We describe the synthesis of poly(glycidyl acetate-co-glycidyl butyrate carbonate)s via the terpolymerization of glycidyl acetate (GA), glycidyl butyrate (GB), and CO₂ by a cobalt salen complex in high atom economy. These new non-cytotoxic polycarbonates are pressure-sensitive adhesives, and peel testing shows the adhesive strength ranges from Scotch-Tape® to hot-melt glues based on glycidyl butyrate content. The tunable adherence, benign degradation products, and facile application and removal suggest their utility as temporary adhesives, such as those used in biomedical applications or medical devices. One polymer, (GA-co-GB)-87, exhibits the proper adhesive strength to sufficiently adhere a collagen buttress to the jaws of a steel surgical stapler and easily release the buttress after firing to successfully cut, close, and implant the buttress into lung tissue in an ex vivo sheep model.

Sequence Control from Mixtures: Switchable Polymerization Catalysis and Future Materials Applications

There is an ever-increasing demand for higher-performing polymeric materials counterbalanced by the need for sustainability throughout the life cycle. Copolymers comprising ester, carbonate, or ether linkages could fulfill some of this demand as their monomer-polymer chemistry is closer to equilibrium, facilitating (bio)degradation and recycling; many monomers are or could be sourced from renewables or waste. Here, an efficient and broadly applicable route to make such copolymers is discussed, a form of switchable polymerization catalysis which exploits a single catalyst, switched between different catalytic cycles, to prepare block sequence selective copolymers from monomer mixtures. This perspective presents the principles of this catalysis, catalyst design criteria, the selectivity and structural copolymer characterization tools, and the properties of the resulting copolymers. Uses as thermoplastic elastomers, toughened plastics, adhesives, and self-assembled nanostructures, and for programmed degradation, among others, are discussed. The state-of-the-art research into both catalysis and products, as well as future challenges and directions, are presented.

Robust Hydrogel Adhesive with Dual Hydrogen Bond Networks

Hydrogel adhesives are attractive for applications in intelligent soft materials and tissue engineering, but conventional hydrogels usually have poor adhesion. In this study, we designed a strategy to synthesize a novel adhesive with a thin hydrogel adhesive layer integrated on a tough substrate hydrogel. The adhesive layer with positive charges of ammonium groups on the polymer backbones strongly bonds to a wide range of nonporous materials’ surfaces. The substrate layer with a dual hydrogen bond system consists of (i) weak hydrogen bonds between N,N-dimethyl acrylamide (DMAA) and acrylic acid (AAc) units and (ii) strong multiple hydrogen bonds between 2-ureido-4[1H]-pyrimidinone (UPy) units. The dual hydrogen-bond network endowed the hydrogel adhesives with unique mechanical properties, e.g., toughness, highly stretchability, and insensitivity to notches. The hydrogel adhesion to four types of materials like glass, 316L stainless steel, aluminum, Al₂O₃ ceramic, and two biological tissues including pig skin and pig kidney was investigated. The hydrogel bonds strongly to dry solid surfaces and wet tissue, which is promising for biomedical applications.

Visible-Light-Curable Solvent-Free Acrylic Pressure-Sensitive Adhesives via Photoredox-Mediated Radical Polymerization

Owing to their excellent properties, such as transparency, resistance to oxidation, and high adhesivity, acrylic pressure-sensitive adhesives (PSAs) are widely used. Recently, solvent-free acrylic PSAs, which are typically prepared via photopolymerization, have attracted increasing attention because of the current strict environmental regulations. UV light is commonly used as an excitation source for photopolymerization, whereas visible light, which is safer for humans, is rarely utilized. In this study, we prepared solvent-free acrylic PSAs via visible light-driven photoredox-mediated radical polymerization. Three α-haloesters were used as additives to overcome critical shortcomings, such as the previously reported low film curing rate and poor transparency observed during additive-free photocatalytic polymerization. The film curing rate was greatly increased in the presence of α-haloesters, which lowered the photocatalyst loadings and, hence, improved the film transparency. These results confirmed that our method could be widely used to prepare general-purpose solvent-free PSAs-in particular, optically clear adhesives for electronics.

Bio-based and Degradable Block Polyester Pressure-Sensitive Adhesives

A new class of bio-based fully degradable block polyesters are pressure-sensitive adhesives. Bio-derived monomers are efficiently polymerized to make block polyesters with controlled compositions. They show moderate to high peel adhesions (4-13 N cm-1 ) and controllable storage and loss moduli, and they are removed by adhesive failure. Their properties compare favorably with commercial adhesives or bio-based polyester formulations but without the need for tackifier or additives.

Mega macromolecules as single molecule lubricants for hard and soft surfaces

A longstanding goal in science and engineering is to mimic the size, structure, and functionality present in biology with synthetic analogs. Today, synthetic globular polymers of several million molecular weight are unknown, and, yet, these structures are expected to exhibit unanticipated properties due to their size, compactness, and low inter-chain interactions. Here we report the gram-scale synthesis of dendritic polymers, mega hyperbranched polyglycerols (mega HPGs), in million daltons. The mega HPGs are highly water soluble, soft, nanometer-scale single polymer particles that exhibit low intrinsic viscosities. Further, the mega HPGs are lubricants acting as interposed single molecule ball bearings to reduce the coefficient of friction between both hard and soft natural surfaces in a size dependent manner. We attribute this result to their globular and single particle nature together with its exceptional hydration. Collectively, these results set the stage for new opportunities in the design, synthesis, and evaluation of mega polymers.

Synthetic globular polymers of several million molecular weight are expected to exhibit unique properties but are difficult to synthesize. Here the authors synthesize such dendritic polymers that show unique lubrication properties and act as molecular ball bearings due to their 3D compact structure, size, solubility, hydration and low intrinsic viscosities.

Sustainable polycarbonate adhesives for dry and aqueous conditions with thermoresponsive properties

Pressure sensitive adhesives are ubiquitous in commodity products such as tapes, bandages, labels, packaging, and insulation. With single use plastics comprising almost half of yearly plastic production, it is essential that the design, synthesis, and decomposition products of future materials, including polymer adhesives, are within the context of a healthy ecosystem along with comparable or superior performance to conventional materials. Here we show a series of sustainable polymeric adhesives, with an eco-design, that perform in both dry and wet environments. The terpolymerization of propylene oxide, glycidyl butyrate, and CO2, catalyzed by a cobalt salen complex bearing a quaternary ammonium salt, yields the poly(propylene-co-glycidyl butyrate carbonate)s (PPGBC)s. This polymeric adhesive system, composed of environmentally benign building blocks, implements carbon dioxide sequestration techniques, poses minimal environmental hazards, exhibits varied peel strengths from scotch tape to hot-melt wood-glue, and adheres to metal, glass, wood, and Teflon® surfaces.